Railway signaling system



C. LE 6. FORTESCUE.

RAILWAY SIGNALING SYSTEM.

APPLICATION man NOV. 6. 1915. RENEWED MAR-21,1919.

1,304,297. Patented May 20,1919.

2 SHEETS-SHEET I.

WITNESSES: v I INVENTOR M Aka/A22 [e5 fir/5550a C. LE G. FORTESCUE.

RAILWAY SIGNALING SYSTEM.

APPLICATION FILED n0v.,s.1915. RENEWED MAR-21, 19x9.

INVENTOR [bar/25 [e6 ffi/"feswe T. h w M 6m m H M mQ m a P a 6w Fw- 7 9 1 4 0 5 1 r/WITNESSE:

ATTORNEY UNITED STATES PAT NT oE rCE.

CHARLEs LE or. EoRTEsCUE, 0F PITTSBURGH, PENNSYLVANIA, 'AssIeNoR T0 WEST- INGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

RAILWAY SIGNALING SYSTEM.

' Specification of Letters Patent. Patented lVIay 20, 1919.

- I Application filed November 6, 1915, Serial No. 59,997. Renewed March 21, 1919. Serial No. 284,176.

provement in Railway Signaling Systems,

of which the following is aspecification.

My invention relates to-electricrailways, and it has special reference to electric signaling systems employed in connection with electric railways wherein the track rails are utilized as return paths or conductors for the propulsion currents.

More particularly, my invention relates to electric signaling systems which comprise a plurality of insulated block sections of track, the block sections being electrically isolated from one another as regards alternating currents having the frequency of the signaling currents but electrically continuous as regards alternating currents having the frequency of the propulsion currents.

When a railway is equipped with an electric signaling system, the track of the railway is usually divided into plurality of insulated block or track sections, each constituting a local circuit for the signaling apparatus associated therewith. Inasmuch as the operation of the separate blocks is independent, the blocks should be insulated from one another as regards the signaling currents. At the same time, the blocks should be electrically continuous as regards the propulsion 7 currents, inasmuch as the track circuit is employed as the return conductor for the propulsion currents. Impedance bonds comprising inductive windings wound upon magnetizable core members and having the terminals of the windings connected to the two rails of a block section and the mid-points thereof utilized for interconnecting adjacent block sections have heretofore been employed for limiting the flow of signaling currents between adjacent block. sections. However, the inductive reactance offered to the flow of the signaling currents by such impedance bonds I is not. suflicient to insure appreciable amounts of signaling current from leaking between adjacent block sections. Such leakage currents frequently interfere with the proper operation of the signaling apparatus of the separate block sections, whereb the signaling devices will sometimes in .icate confine to their respective block sections when'an installation comprises a plurality together to provide alow-impedancepath for the return flow of the propulsion currents. When a rail of a block or track section breaks, the leakage area afforded the broken rail by reason of the corresponding block sections of the other track circuits electrically bonded thereto, is frequently sufficient to permit the signaling devices to operate as though normal conditions obtained upon thetrack. In this instance, it is essential that, when a rail breaks, the signaling circuit of the associated block section be interrupted in order that danger may be indicated to an approaching train.

One object of my invention is to provide means in an electric railway system whereby the block sections may be electrically isolated from one another as regards the signaling currents, the two rails of the track circuit, at the same time, jointly constituting a common conductor for the return flow of the propulsion currents and between which the propulsion currents will divide equally.

Another object ofmy invention is to provide means in an electric railway system to provide a path oflow impedance for the return flow of the propulsion currents and, at the same time, the insulated blocksections may be electrically isolated from one another in order that the signaling devices may indicate-the actual conditions only obtaining upon the several track circuits- Fora better understanding of the nature and scope of my invention, reference may be had to the following description and the accompanying drawings in which-Figure 1 is a diagrammatic representation of a singlephase railway system embodying a form of my invention; Fig. 2 represents a railway system comprising a plurality of track circuits which are bonded together, each comprising electrically isolated block sections, and Fig. 3 is a modified form of the system shown in Fig. 2; Y

Referring to Fig. l;

railway system,

of parallel track circuits which are bonded comprising a single track 1 and a trolley conductor 2, is supplied with propulsion currents of a certain frequency, such as 25 cycles, from a source of alternating-current supply shown as a single-phase alternator 3. The track 1 comprises a plurality of insulated block sections l which are separated from one another by means of insulating joints 5 inserted in the rails of the track. Each of the block sections 4 is connected, through track transformers 6 and 6 to a signaling circuit 7 which supplies power to operate a signaling device 8. Since the block sections are electrically insulated from one another, as reg ards the signaling currents, impedance bonds 9 are employed to afford means for interconnecting the block sections to one'another'in order'to provide a return path for the propulsion currents. The impedance bonds 9 are of the usual form of construction and comprise inductive windings on iron cores, the terminals of the windings being connected to the two rails of a traok section. Taps are positioned at the mid-points of the windings to afford means for interconnecting adjacent'block sections to one another through a primary winding 10 of a transforming device 11.

The winding 10 of the device 11 is preferably disposed on a magnetizable core member (not/shown) and loosely magnetically linked with a secondary winding'12 which, in turn, is connected" in closed circuit with a condensive reactance element 13. The relation between the capacity reactance afforded by the'condensive element 13 and the internal reactance of the transformer is so adjusted that the primary winding 10 constitutes a' resonant path for alternating currents having the frequency of the propulsion currents only.

Under normal conditions of operation, the signaling currents flow in'a local circuit constituting the track section 4, a winding 14 of a signaling relay device 15 and a'winding 16 of an inductive reactance element 17. Another winding 18 of the relay' device 15 is energized by means of the track transformer (i Under these conditions, the signaling device 8 indicates that the block section 4 is open. When a train 19 bridges the rails of the track section 4, the signaling currents are shunted from the winding 1 1 of the signaling relay 15, and the signaling device 8 indicates that a train occupies the block section.

The propulsion currents return to the generator 3 through the track, the windings of the impedance bonds 9 assuring that they will be equally dividedbetween the two rails of'the track, therebyprecludi'ng circulating currents of the propulsion frequency from flowing in the lo'cal circuit established by the block section 4/ At the same time, the electrical conditions obtaining in the wind ing 10 of the transformer 11 provide an unimpeded path to the flow of the propulsion currents only since the winding 10 constitutes a voltage-resonant circuit tuned to the frequency of the propulsion currents. Moreover, the signaling currents are confined to their respective track sections, inasmuch as the winding 10 inserts an inductive reactance that opposes the flow of alternating currents having the frequency of the signaling currents. In consequence of the impedance afforded" by the windings of the impedance bonds "9 and the"'hig'h in rpedance devices 11, the signaling currents areprecluded from flowing between acent track sections and, therefore, the signals 8 arcinfli lleed n h n h pi bpe d qfi 1btain upon'the block sections which they are desigii'edto protect. i

Referring'to Fig. 2, I have shown my invention asconsisting of track bonds that interconnect several parallel tracks to provide a path oflow impedance for the return flow of the propulsioncurrents. The railway system comprises tracks'19, 20. and 21 which are'c'onnected to one terminal of an alternator 22 shown asa-sing lephase generator.

Trolley conductors 23, associated with the tracks, are connected to'theother terminal of the generator 22. The tracks 19,20and21 are shown as divi'ded into a plurality of in sulated track sections 24 by insulating joints 25 insertedin the 'railsthereof. Impedance bonds'26, of a usual'formofconstruction, are placed on both sides of the insulating joints '25 to'connect the two rails of each track section to each other in a manner well known in the art. "Each of theimpedance bonds 26 is provided with a tap atit's'mid point, thus affording means forinterconnecti'ng "successive block sections of "a track to one another. The severaltracks 19, 20 and 21 are iiiterconn'ected'by track bonds 27 which extend between the taps of corr'espending imp'edan'ce'bond's, such as 26 and 26. A signaling circuit 28 is connected, through m-ack'transformers 29, 30 and 31, to the tracks 19, 20' and 21,"respecti,vely, but, for the purposes of illustration, I have shown only the" track 21 equipped with. a signaling device 32 which is operated in a well known manner by means of a signaling relay 33. It 'will be understood, however, that it is usual to equip each block sectionof the/"several tracks with signaling apparatus. It is important, therefore,'that the block sections' be'elec ti'ica lly' isolated from one another in orderthat 'thes'ignaling device 32 shall be influenced only by "ti afiid'conditions u on the "in ulated block Scents 24 of an track'2'1." The relay device 334compris es an inductive winding 34 which is connected across the rails o'f'theasso'ciated track section '24 and a second inductive" "winding 'gfi'wliich is" connected in closed circuit with a secondary winding 36 of a track transformer 37. Assume, for instance, that a rail section 38 breaks at 39. It is important, under this circumstance, that the signaling device 32 shall indicate dangeiyand, normally, this will be the case, inasmuch as the circuit through the inductive winding 34 of the sig naling relay 33 will be interrupted. 'Since, however, the tracks 19, 20 and 21 are bonded together, there is danger that the leakage current flowing between-the two portions of the broken rail 38 will be sufficient to energize the winding 34 and, in this-instance, the signaling device 32 will indicate safety when, in reality, a broken rail exists in the associated block section. To preclude the occurrence of such large leakage signaling currents, the track bonds 27 are so designed that-they offer an extremely high impedance to the flow of alternating currents having the frequency of the signaling currents. At the same time, they permit an unimpeded flow of the propulsion currents, inasmuch as the propulsion currents divide between the several tracks which, in combination, comprise the return path therefor.

Each track bond 27 comprises a primary winding 40 having its terminals connected to the mid-points of the corresponding impedance bonds 26 and 26 inserted in the adjacent track circuits 20 and 21, a secondary winding 41, which is loosely magnetically related to the primary winding 40, and a condensive reactance element 42, preferably of constant capacitance. The condensive reactance aflorded by the condenser 42 exactly counterbalances the inductive reactance occasioned by the leakage magnetic flux between the primary winding 40 and the secondary winding 41. As a result, resonant conditions obtain in the circuit comprising the primary winding 40 for alternating currents having the frequency of the propulsion currents only. While the track bonds 27 afford a free flow to alternating currents having the frequency of propulsion currents, they offer a high impedance to alternating currents having the frequency of signaling currents, inasmuch as they are tuned to the frequency of the propulsion currents only.

Since the signaling currents flowing in the tracks 19 and 20are substantially precluded from flowing into the track 21, the block section 24 of the track 21 is electrically isolated as regards the signaling currents traversing other block sections. As a consequence thereof, the signaling device 32 will, at all times, indicate the actual conditions obtaining on the track 21. Again, the leakage area of a broken rail in any one block section is so limited that the local circuit which constitutes the broken rail will be interrupted.

In Fig. 3, I have shown a railway system embodying the apparatus utilized in the eye tem shown in Figs. 1 and For the purpose of illustration, Ihave shown a'single block section 43 equipped with the signaling device 32 that is operated, as hereinbefore explained, by a signaling relay 33. The

electrical circuits comprising the signaling apparatus have been fully explained and, therefore, I do not deem it necessaryto give a detailed description of the operation of the signaling equipment. The railway system of Fig. 3 comprises a plurality of tracks 44, 45 and. 46 and trolley conductors 47. Power is furnished to the several trolleys for propulsion purposes by means of a singlephase a1ternat0r'48. The signaling circuit 28 is connected to each track through track transformers 49, 50 and 51. As hereinbefore explained,'each of the tracks constitutes a plurality of insulated block sections formed by the insulating joints 25. Impedance bonds 26, of the charactershown in Figs. 1 and 2, are positioned on both sides of themsulating joints 25 in order to provide means whereby the propulsion currents may flow through successive block sections. Adjacent impedance bonds are connected to one another through transforming devices 1-0 which, as explained in connection with Fig. 1, constitute resonant circuits for alternating currents having the frequency 'of the propulsion currents only. In this manner, the signaling currents are precluded from flowing between adjacent block sections of each track; y In order to provide a low-impedance path for the return flow of the propulsion currents, the tracks 44, 4'5 and 46 are bonded together through transforming devices 52. It'will be noted, by referring to the transforming device connecting the track circuit 44 to the track 45,.that a primary winding 53 thereof is connected at 54 to the primary winding 10 of the transforming device 11. The other terminal of the prlmary winding 53 is connected at a point 55 which is diagonally opposite to the side of the primary winding 10 of the transforming device 11 to which the first terminal of the primary winding 53 is connected. The transforming. devices 52 are diagonally connected, as mentioned above, between corresponding. block sections of the several tracksin order that the leakage currents which may influence the'signa'ling devices of a block section may be minimized to a negligible quantity, as will be hereinafter explained. A

Referring to the construction of the transforming devices 52 which are employed as track bonds, each comprises a primary winding 53 and two secondary windings 56 and 57, the winding 56 being closely magnetically linked to the winding 53, and the winding 57 bein loosely magnetically linked to the win ing 53,. The Winding 5615 connected in closed circuit with a eondensive reaetanes element 58, and the secondary winding 57 is connected in closed circuit with a condensive reactance element 59. The capacity of the condenser 59 is so selected that,.in combination with the inductive reactance occasioned by the magnetic leakage between the primary winding 53 and the secondary .wind ing 57, resonant conditions maybe established in the primary winding 53, as regards alternating currents having the frequency of the propulsion currents only. In this manner, the track bonds provide unimpeded paths to the flow of. the propulsion currents. Again, the capacity of the condenser 58 is so selected that, when alternating-current impulses haying the frequency of the signalingv currents are impressed uponthe primary winding 53, current-resonant conditions are establishecttherein, thereby precluding an interchange of alternating currents having the frequency of the signaling currents between corresponding block sections of the track circuits. A more detailed description of the transforming device 52 is given my co-pending application, Serial No. 61088, filed Nov. 12, 1915.

Assuming that a rail section 60 breaks at a point 61, since the several tracks are supplied from the common signaling circuit 28, signaling currents will tend to flow in the block section A3 because of the interconnection existing between the corresponding block sections of the several tracks. Signaling currents flowing from a corresponding block section 45. of the track 45 will have to flow through a transforming device 11 each of which afl'ords an extremely high im pedance. Therefore, leakage currents from corresponding block sections of the other tracks will be substantially precluded from flowing in the disabled block section 13. As a result, the. signaling device 32 will indicate danger when the rail section 60 breaks because the local circuit will be efiectively interrupted.

WVhile I have shown severalembodiments of my invention, it will be apparent to those sl rilled in the art that additional modifications may be made without departing from the spirit and scope of the appended claims.

I claim as my invention:

1. An electric railway compr sing a track, insulating joints inserted at spaced intervals therein to form a plurality of insulated block sections, inductive windings connected across the rails on both sides of the insulating joints, taps at intermediate points of the inductive, windings, and resonant circuits for connecting the taps of adjacent inductive windings to one another.

2. An electric railway comprising a track dividedinto a plurality of insulated track sections, and means for so connecting the track sections tonne another that the pro,- ralsi ae ir st "as qua y. riser be tween the two rails of .the track and current haying the. frequency of the propulsion current only may flow unimpeded through successive track sections.

3. An electric railway comprising a track divided into a plurality of insulated track sections, impedance bonds for connecting the rails of each track section to one another 7 ing propulsion current may be equally divided between the two rails of the track and flow unimpeded through successive block sections, and track bonds electrically con.- necting the tracks to one another which constitute resonant circuits tuned to the frequency of the alternating propulsion current only.

5. An electric railway system comprising a plurality of tracks which are electrically continuous as regards the alternating propulsion current only, and track bonds interconnectingsaid tracks to one another which constitute impeded paths for the flow of alternating currents haying frequencies other than that of the propulsion current.

6. An electric railway system comprising a plurality of tracks divided into insulating track sections, means for so connecting the rails of the track sections to one another that the propulsion current may be equally divided between the two rails of the track and the track sections may form an electrically continuous circuit of low impedance as regards alternating current having the frequency of the, propulsion current only, and track bonds interconnecting the tracks which constitute resonant circuits for alternating currents having the frequency of the propulsion current only.

7. An electric railway system comprising a plurality of tracks divided into block sections, means for supplying each block 'section from a common source of signaling-current supply, and track bonds interconnectingthe block sections of the several tracks to one another which constitute unimpeded only for connecting the block sections of rents having the frequency of the propuleach track in continuous series relationship, sion current only. and track bonds ,connected between said In testimony whereof, I have hereunto l0 resonant circuits to connect the block secsubscribed my name this 26th day of Oct. tions of the several tracks to one another, 1915.

said track bonds constituting resonant circuits for the free flow of alternating cur- CHARLES LE G. FORTESOUE.

Copies 01' this patent 1 nay be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G. 

